The present invention relates to the preparing of sewing data for an embroidery sewing machine. More specifically, the present invention relates to a sewing machine that forms an embroidery pattern on a work by causing the relative movement between a vertically movable needle and the work based on needle location data showing the relative position of the needle and the work or based on block data that is related to the needle location.
A data preparing apparatus is disclosed in Japan Published Unexamined Patent Application No. 58-198375. In this related art, a drawing showing an embroidery design is adhered on a tablet board. An operator defines multiple closed areas for dividing the design. When the operator designates multiple points on the outlines of the defined closed areas with a cursor, the outlines of the closed areas are stored as defined. The needle location data for embroidering each stored closed area can thus be computed.
The needle location data is computed by moving a predetermined straight line parallel with a stitch-forming direction, sequentially obtaining intersections where the closed area outline and the straight line meet, and selectively storing the intersections as the needle location data.
Another data preparing apparatus is disclosed in Japan Published Unexamined Patent Application No. 63-132690. In this related art, the image of an embroidery design is picked up with a TV camera and displayed on a CRT. An operator designates given points on the outline of the displayed image on the CRT and sets the outline. Subsequently, the operator designates a dividing line for dividing the outline. When designating given points and dividing lines, the operator may use, for example, a light pen. The image of the embroidery design is thus divided into polygonal closed areas. Vertexes of the closed areas and other location data are sequentially computed and prepared as block data that is related to the needle location (hereinafter referred to as the block data). The needle location data indicating actual needle locations is then computed based on the block data and a predetermined stitch density data.
In these related arts, the operator must define the closed areas dividing the embroidery pattern and designate coordinate data such as vertexes of the closed areas with the cursor, the light pen or the like so that the defined closed areas are set and stored. When the closed areas are set, the data preparing apparatus computes and prepares the needle location data.
In the related arts, however, the operator must manually set the closed areas according to the configuration of the embroidery pattern. The setting of the closed areas is a troublesome and time-consuming operation. At the same time, the operator must set the closed areas having a configuration such that the computation of the needle locations is possible. The operator must be experienced in setting the closed areas. In the related art disclosed in Japan Published Unexamined Patent Application No. 58-198375, for example, when the operator sets an almost U-shaped closed area the closed-area outline and the straight line might meet at three or more intersections. Therefore, the needle location cannot be computed.